Many efforts have been made to produce fuels for barbecuing that are clean-burning, easy to handle, and easily ignitable. Charcoal, usually made from a wood base, is the most common component of fuels for barbecuing. Charcoals having vegetable and coal bases have also been used. Such fuels are difficult to ignite for cooking and often require the use of an ancillary flammable material, such as lighter fluid or newspaper, to create a flame of sufficient duration for the charcoal to ignite.
Previous innovations have involved the impregnation of charcoal with a more flammable compound, such as lighter fluid (or other volatile fluids, such as higher alkanes), waxes, or other oxidants that burn faster and more readily than charcoal. These penetrate only the outer surface of the charcoal. Those including volatile components or that are very easily oxidized are susceptible to dissipation over time, greatly reducing the effectiveness of those fuels. Other processes create a mixture of charcoal and an ignitable material, ultimately forming a homogeneous material that, overall, should be easier to burn. The point, however, of utilizing easily ignitable material is to achieve the initial burning of the charcoal. Once the charcoal reaches a certain level of combustion, it burns without further aid. Mixing the ignitable component throughout the fuel adds little overall benefit, because the benefits of ancillary ignitable components are superfluous once the combustion of the charcoal is underway. The use of volatile or easily combustible components throughout such fuels produces fumes during combustion, which may impart undesirable flavors to food cooked using such an article. Such fumes would be given off during the entire burning time, which is a considerable drawback to these types of fuels.
Another consideration for combustible fuel is efficient burning. Some fuels release a very large amount of heat during the initial stages, which tapers off to a much lower release rate during the time appropriate for cooking. It would be more efficient, and perhaps safer, to have a fuel whose heat release rate during ignition was less than the release rate during the optimal cooking time. In this way, the heat generated by a fuel would not be wasted in the startup process, but could be utilized in the form of longer cooking times.
By way of example, one commercially-available charcoal-based fuel exhibits the heat-release profile shown in FIG. 1. The graph depicts the rate of heat release per area of material. The graph peaks at 300–350 kilowatts per square meter during ignition of the material, dropping to a steady-state heat-release rate of approximately 40–50 kilowatts per square meter. This represents an initial ignition stage in which a large amount of heat is released very quickly before the release rate ramps down to a state in which cooking is appropriate.
The following prior art reflects the state of the art of which applicant is aware and is included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
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Kim teaches a three-layer combustible fuel article, comprising three distinct layers: a fire-igniting layer, a fire-catching layer, and a body layer. The body layer contains carbonized wood and a starch binder, and the other layers include less carbonized wood and more easily-ignitable components. Also included are optional air holes and optional grooves for visual appeal. Inter alia, Kim specifically recites that “No coal is used in the combustible articles.” (col. 2, line 12)
The remaining citations diverge even further from the nexus of the instant invention.